A production step of a conjugated diene polymer obtained through solution polymerization generally includes a step of bringing a conjugated diene polymer solution obtained after polymerization into contact with a large amount of steam, thereby evaporating a solvent. Moreover, there is also proposed a method for devolatilizing a solvent through heating while conveying a conjugated diene polymer solution with a screw using a screw type apparatus such as a biaxial extruder or kneader without bringing steam into direct contact with the conjugated diene polymer solution. For example, Patent Literature 1 discloses a devolatilization apparatus and a devolatilization method each using an extruder. Moreover, Patent Literature 2 discloses a method for extruding a resin at a low temperature and at a low pressure with an extrusion apparatus having two screws by injecting a supercritical fluid in devolatilizing a solvent.